Electric discharge apparatus



July 15, 1941.

| D. MILES I 2,249,485

ELECTRIC DISCHARGE APPARATUS Fildsept. 16, 1939 22 Ifiventor: Lawrencj D. Miles 6. b9 WW? His Atfiorneg.

Patented July 15, 1941 UNITED v T S PM ENT 1 OFF-ice 2,249,485. ELECTRIC DISCHARGE APPARATUS Lawrence D.- Miles,'Ballston-Lake.N. Y., assignorto General Electric Company, a. corporation of- New York- Application-September 16, 1939. Serial No. 295,325

scr ams. (01. 250-275) My invention relates to electric dischargeapparatus or electric valve means and more particularlyto circuits for controlling theoperation oi apparatus of this nature.

It'has been proposed heretofore to initiate arc discharges between the anode and the cathode of electric valve means by employing an immersionignitor or make alive control member which is associated with a pool type cathode; such asja mercurypoolcathode; The term poo as' used herein and in the appendedfclaimsis not limited to liquid metals such as mercur'ylbut' is intended also to-include solid substances which are'capable" of analogous use. Particular; examples .of such solidsubstances arecadmium.andbismuth. The

initiationyof the arc discharge between-the oathode andthe anode is effected by, transmitting to the controlmember current of a magnitude 'sufil cient to establish on thesurface of the cathode a potential gradient of a value which initiates the such as boron-carbide or silicon-carbidahaving a specific electrical resistivity largecompared with that of the associatedpool cathode. 2 Due to the natureofthe materials Whichhave-been found most efiective in the initiation of arc discharges,

5.1icuits forele'ctric valve means of the type e'mpl'oy new andimproved control system'forelectric valve apparatus.

It is a further object of my invention -topro-- vide new and improved control or excitation ciring anionizable medium and havinga p001 cathode.- 1 ff' 1mm still further object drmy mvennon a providea newand improve'd arc-initiating and IO arc-maintaining circuit for-electric valvemeans '26- establishment of a cathode spot. The make-alive": electrode is, preferably, constructed, of a material,

of the type employing a' mercury 'pool cathode and-an immersion-ignitor control member. 1 Briefly described, in accordance with the illustrated embodiment ot my invention, Ipro'videa "15 new and improved control circuit for an electric valve means of the type employing an'ioniz'able medium} such as mercury vapor, and including a mercury pool-cathode "and an associated immer si'on-i'gnitor control member. Theexcitationor the cathode to initi ate'an arc discharge; and apparatus provided 'tomaintain an arc discharge within the electric valve means-atter'the initia Wanner "the discharge, thereby relieving the duty it is important to relieve as much as possiblethe.

dutydmposed-on the material by requirihgth control member to conduct current .only until the arcdischarge is initiated and to. interrupt (or dee if crease substantiallyv immediately thereafter the; currentconducted by the control member. I r1 this manner, the life oi the control member-and the life of the ,electric Valve means are materially.

increased; It'has also been appreciated heretoe fore that'it is desirable to limit or substantially eliminate the magnitude of the negative or inverse voltage which'is impressed across the controlmember and the cathode. Antappreciabl inverse voltage and consequential inverse current have-been found .to have a deleterious: effect upon the life of the control member In accordance with the teachings ofmy invention disclosed herefor effectively controllingan electric valvemeans ofthe pool type-employingmake-alive or'imm'ersion-ignitor control members; and which relieves the dutyimposed? on" the; control 'mem-ber'so 'that' thelifeof'the electric valve means is'substan tially increased.

It'is an object of my inv to p v new and improved electric discharge apparatus. 1

It is another object of my invention to provide a inafter, I provide new-and :improvedapparatus A imposed on the control rnember and increasing the life of the apparatus- V 'For 'a better understanding-of my; invention,

referencemay be had-to the following d'esc'ripg' -tion,takenin connectionwith the accompanying drawing and its scope will be pointedoutin the appended'claims. The'single figure diagram-'1:

manca11y-i11useates an embodiment of my in vention as applied to a mercury-poolelectric dis-f: 35- -charge device having a make-alive or an immersion-ig'nitortype control member.

Referring particularly to thesingle fi'gure of the accompanying drawing, I have chosen to represent niy invention'as applied to an electric dischargedevice-or an electricvalve means compris-if ing'a metalenvelope I forming an enclosedgdischarge space within which are arranged an anode 2 anda pool cathode 3,"such" asa mercury-pool V cathode, forming with'the anode 2 ap''propriate discharge terminals. The electric discharge device may-incorporate some hf the features' dis closed and claimed in UIIS. Letters Patent No 2,152,201- granted L/lIarch28Q-1939 ulion rnyap plic'a't'i'on and whichis assigned to the assignee a: the presentappli'cationj Oneofjth'ese features may be the apparatus there shown tor confining; the cathode spot within a limited desiredregion on the 'surface of the mercurypool. This confim L ingmeans may *comprise' a shield 4- ofcy1indric l] configuration and constructed of a refractory control' system transmits a relatively large imp'ulseof-current through the control memberftof material adapted to withstand the effects of an arc discharge. The lower portion of the shielding member is also preferably of a refractory metal or a ceramic material. In order that the oathode spot maintained within the shielding member may be effective to initiate a discharge upon the application of suitable voltage differences between the anode 2 and the cathode 3, at least some communication must be provided with the inner chamber of the shielding member and the main arc discharge path. The shielding member, therefore, is provided with a plurality of longitudinal slots or openings 6 formed in the shielding member. These slots 6 preferably extend normally or perpendicularly from the cathode surface to a point appreciably above the surface.

It is possible, of course, to arrange the cathode construction in a number of ways. However, I prefer an arrangement such as that shown in the figure wherein the assembly as a whole is mounted on a demountable header 1 which is positioned within a conforming cylinder 8 extending from the bottom of the envelope l. The header is secured in place by an externally accessible fillet 9 of appropriate sealing material such as glass or fused metals which may be removed or broken away to permit replacement or repair of a header whenever necessary. The power or cathode terminal of the electric valve means may consist of a suitable metal connection In in electrical contact with mercury pool cathode 3.

To initiate an arc discharge within the electric valve means or more particularly within the inner chamber of the shielding member 4, I employ a control member I l of the make-alive or immersion-ignitor type having an extremity thereof extending below the surface of the mercury pool cathode 3 and being constructed of a suitable material having an electrical resistivity relatively large compared with that of the associated mercury of the cathode 3. r This material may be boron-carbide or silicon-carbide, as stated above, or any other suitable material of this nature. I provide a holding structure or support 12 for maintaining the immersion-ignitor control member -II in operative relation with the cathode 3. The support I2 is arranged not only to act as a mechanical supporting structure for the control member I I, but is also arranged or adapted to operate as a holding anode to maintain an arc discharge between itself and the cathode 3 upon the initiation of an arc discharge by the transmission of a suitable current through the control member H. The support 12 may be constructed in cylindrical form to support the upper portion of the control member H, and is preferably constructed of a material such as tungsten, molybdenum or graphite capable of withstanding an arc discharge without appreciable disintegration. A terminal connection for permitting the makealive electrode and the support l2 to be energizedis shown at I 3. This stem-like construction may extend downwardly and is attached to a terminal M which isarranged toeffect transmission of arc-initiating current and arc-holding current to the control member II and to the support I 2, respectively.

In order to illustrate in simplified form a circuit application for the electric discharge device, I have chosen to show the discharge device connected for energizing a load I 5 from an alternating current supply circuit comprising conductors ltand l1. Unidirectional current is transmitted to the load l5 through the electric discharge device.

I provide a control or excitation system for transmitting to the immersion-ignitor control member H an impulse of current of sufl'icient magnitude to establish an arc discharge within the electric valve means. More particularly, an impulse of current is transmitted through the control member H to the cathode 3 to establish within the chamber provided by the shielding member 4 an arc discharge. This excitation circuit is arranged to decrease substantially the energization of the immersion-ignitor control member H as soon as an arc discharge is initiated. I provide a control or excitation circuit responsive to the voltage applied across the anode and cathode of the electric valve means to effect energization of the control member I I. This circuit is responsive not only to the magnitude of the anode-cathode voltage, but is also responsive to the polarity of the anode-cathode voltage so that energization of the control member is effected only when the polarity of the voltage is suitable for initiating an arc discharge between the anode and the cathode. excitation circuit operates to maintain an arc discharge within the inner closure of the shielding member 4. after the initiation of the discharge. In the event the arc discharge is not maintained within the closure, the circuit be-.

comes effective to cause re-energization of the control member II to initiate another discharge. 7

Referring more particularly to the arrangement shown in the drawing, I provide a control or excitation circuit comprising a suitable unidirectional conducting device, such as a copper-oxide rectifier l8 disclosed and claimed in U. S. Letters Patent No. 1,640,335, granted August 23, 1927 upon an application of Lars O. Grondahl. I also provide-a suitable inductive. device, such. as a.

transformer l9 having a primary winding v2!! and a secondary winding 2|. The primary winding 20 is connected in series relation with the copper-oxide rectifier l8 across the anode 2 and the cathode 3 through terminal ID of the electric valve means. One terminal of the secondary winding 2| is connected-to terminal l4 associated with the control member II and the support l2. The other terminal of the secondary winding 2| is connected to a suitable source 22 of unidirectional current for maintaining an arc discharge within the closure of the shielding member 4 after the initiation of the discharge. The voltage of circuit 22 is unidirectional and of a value substantially less than the magnitude of the voltage impressed upon the control member II to effect initiation of the arc discharge. I have found that the source of voltage 22 may have a value of substantially 20 or 30 volts. The source 22 applies to the support I 2 a suitable unidirectional voltage through secondary winding 2| of transformer. l3, so that the support'l2 operates as a holding anode once the arc dischargeis estabstabilizing or limiting this current, I provide a stalilizing means such as a stabilizing resistance 23 connected in series relation with the support l2 and the source 22. Instead of a resistance'as a stabilizing means, I of course may use an 'inductance. a

The operation of the embodiment of my invention shown in the single figure of the drawing will be explained by considering the system Furthermore, the control or,

when the electric; .valve means; zlS operating ,to

' r gion-ma. 1 1 21 3 1? 41 transmit unidirectional-current ito; thepload 5" 5 fromgthe alternating current supplycircuit [6,11 13- Upon ,energization of the alternating current eir the electric valve means. During the; first; posi-q, tive half cycle of: appliedanode-cathode voltage; Q.

the control or excitation circuitoperates to;tra;ns-..

mit an zimpulsepof unidirectionalacurrent to-the immersion-ignitor control pmembergl I; The; con-;.

trolor excitation icircu t, isince it 1, is. responsive to the polarity of-theranodeecathode voltage; due.

to the presenceof the copper-oxide:rectifier18y;v eiiects' energization of-:the; control-,member- H only during-J1 the positive rhalfi cycles; of anodeing member 4 until the; anode--cathode:.=voltage increases to a valuewhich. is suflicient to trans:

mit the-desired or. required value-of current to the control memberll; When thisvaluev of anode-cathode voltage, is attained,.;animpulse of current will be transmitted through .the controlmeanswill substantiallydecrease from itsimtial value touthe :valve'voltage drop due to the fact will flow trol member; I l: ffor,, two;;reasons.; In, the first place; the: small .Value; of reverse; orv inverse current Which-flows;throughqthe copper-oxide rectifier 5| 8; during the-negative halt-cycles ofanode- :cathode: voltage; is gabsorbedas excitingL current in: the transformer cl 9: and this value of exciting current; is: ineffective ,tO' buildup an appreciable secondary voltage. In the second place, there isimpressed;on.the,control member II a positivevoltage .at :all -.times byithe unidirectional voltage. source 22.; Another of the-.principaleadvantages. ofmy invention is the manner in which I the .excitationasystem relieves the. duty. imposedv on .the, control memberby effecting deenergization of the. control. memberlas. soon as an arc dischargezisestablished between the anodeZ and the cathode3. Moreover,.the absence of inverse voltage also materially increases the life of the control member and :the discharge device.

5;; While I have shown-and described my invenmember- H and the mercury pool .cathode13 to establish an arc discharge within the closure of-. the shielding member'4. 'Immediatelythereafter, the,-anode-cathode voltageof the electricivalve that an arcdischargewill 'beestablished between the main-anode .2 and the cathode 3." The volt' age then impressed across the primary winding 200i the transformer l9 and the copper-oxide rectifier I'B will be. the arcdropof theelectric valve means. It'will beunderstood that the-application of apositiv'evoltage to themain anode 2 establishes within the vicinity thereofa strong positive electrostatic field which draws electrons from the c'athodespot within the closure of the shielding member 4 through the slots .65 That is, the electrons are drawn through the slotB to establish a cathode spot outside theshielding member 4 and in:turn to establishja main arc discharge between the anode 2 and the oath-- ode-3.:

After the cathode spot is initiated within the shielding .member Ajdu'e to the application of theunidirectional :voltage tothe support l2 and the relatively-"larger resistance of the control member 1 l thearc discharge is'transferred from-- the control member H to the support I2 which acts as a holding anode; The magnitudeof the voltage'applied to the control member H to inihundred or three hundred volts, whereas the arc discharge may be maintained by a much smaller voltage, such as twenty or thirty volts, after the initiation of the discharge.

It is to be understood that after an are discharge has been initiated within the shielding member 5. it is maintained therein by the support l2 which operates as a holding anode. Circuit 22 supplies the holding current. During each positive half cycle of applied anode-cathode voltage, current will be conducted between the anode 2 and the cathode 3. the positive half cycle at which anode-cathode current begins to flow, of course, depends upon the instantaneous value of the anode-cathode voltage. As soon as the voltage reaches that value where the field provided by the anode 2 is suficient to draw more than the critical numtions may:beg'madeizwithout. departing from my invention,-=and :I," therefore, aim. in' the appended claimsto cover all such-'ichanges and modificationsas =fall withinithe true spirit-and scope of myinvention. M

Letters Patent-10f the United States, is: a

1. 1 In combination, an electric valve means having. an-.anode, a cathode of-the pool type, a'controLmember of the immersion ignitor type aseoz-sociate'd withsaid cathode and a support for maintaining said control memberin operative relation with said cathode,"means for supplying to said-control member a voltage suificient to ini-tiatean are discharge between said anode and isaid cathode, and means -for supplying to said supporta voltage of a magnitude insuificient in itself to initiate an arc discharge butsufiicient to maintainan arc discharge within said electric valvemeans afteran arc discharge has "been 0i established by the;

energization ,of said control member. a V

2. In combination, an electric valve means having arranode, a'cathode of the pool type, a control; member of, the immersiomignitor type assoi ciated with said cathode and a support for maintiate the arc discharge is in the vicinity of two The exact point in her of electrons through the slots 6 into the 7 taining said control memberin operativerelation control member a voltage sufficient to initiate an arc discharge between said anode and said cathode when said electric valve means is nonconductive, and means for supplying to said support a unidirectional voltage of a magnitude insuflicient in itself to initiate an arc discharge but sufficient to maintain an arc discharge within said electric valve means after an arc discharge has been established by the energization of said control member.

3. In combination, an electric valve means having an anode, a cathode of the pool type, a control member of the immersion-ignitor type associated with said cathode and a support for maintaining said control member in operative relation with said cathode, means responsive to the voltage appearing between said anode and cathode for supplying to said control member an srhar e pa h; d schar e s initiated-- .in that; path ;and .current will Whatl claim as newand desire to secureby 3 impulse of voltage to initiate an arc discharge between said anode and said cathode, and means for supplying to said support a unidirectional voltage of a magnitude insufficient in itself to initiate an arc discharge but sufiicient to maintain an arc discharge within said electric valve means after an arc discharge has been established by the energization of said control member.

4. In combination, an electric valve means having an anode, a cathode of the pool type, a control member of the immersion-ignitor type associated with said cathode and a support for maintaining said control member in operative relation with said cathode and adapted to operate as an auxiliary holding anode, means responsive to the voltage appearing between said anode and said cathode for initiating an arc discharge between said anode and said cathode, and means comprising a source of unidirectional voltage of a magnitude insufiicient in itself to initiate an arc discharge but suflicient to maintain an arc discharge between said support and said cathode after an arc discharge has been established by the energization of said control member.

5. In combination, an electric valve means having an anode, a cathode of the pool type, a control member of the immersion-ignitor type associated with said cathode and a support for maintaining said control member inoperative relation with said cathode and being adapted to operate as a holding anode, means responsive to the magnitude and polarity of the :voltage appearing across said anode and said cathode to initiate an arc discharge therebetween by effecting energization of said control member and comprising a transformer having aprimary and a secondary winding and a unidirectional conducting device connected in series relation with said primary winding across said1anode and cathode, and a source of direct current for impressing on said support, a unidirectional arc-maintaining voltage through said secondary winding.

6. In combination, an electric valve means having an anode, a cathodeof the pool type, a control member of the immersion-ignitor type associated with said cathode and a support for maintaining said control member in operative relation with said cathode and being adaptedto operate as a holding anode, means for transmitting to said control member an impulse of.

current to establish an arc discharge between said anode and said cathode, andmeans for maintaining an arc discharge within said electric valve means between said support and said cathode after the initiation of a discharge by the energization of said control member comprising a source of unidirectional current for maintaining said support at a potential positive with respect to said cathode. v

'7. In combination, an electric valve means having an anode, a cathode of the pool type, a control member of the immersion-ignitor type associated with said cathode and a support for maintaining said control member in operative relation with said cathode and being adapted to operate as a holding anode, means responsive to the magnitude and polarity of the voltage appearing across said anode and said cathode to initiate an arc discharge therebetween by eflecting energization of said control member, means comprising a source of unidirectional current for energizing said support to maintain an arc discharge between said support and said cathode, and a stabilizing resistance connected in circuit with said support and said source to assure the transmission of a substantially constant unidirectional current between said support and said cathode.

8. In combination, an electric valve means having an anode, a cathode of the pool type, a control member of the immersion-ignitor type associated with said cathode and a support for maintaining said control member in operative relation with said cathode and being adapted to operate as a holding anode, means for supplying to said control member an impulse of voltage sufiicient to initiate an arc discharge between said anode and said cathode, and means for supplying to said support a unidirectional voltage of a value relatively small compared to the magnitude of said first mentioned voltage to maintain an arc discharge between said support and said cathode.

9. In combination, an electric valve means having an anode, a cathode of the pool type, a control member of the immersion-ignitor type associated with said cathode, a support for maintaining said control member in operative relation with said cathode and being adapted to operate as a holding anode and a shielding member for substantially enclosing said control member, and said support for confining the cathode spot upon a localized area of said cathode and having openings therein for permitting the establishment of an arc discharge between said anode and said cathode upon the application of a positive voltage to said anode, means for transmitting to said control member an impulse of current for initiating an arc discharge within said shielding member, and meansfor supplying to said support a voltage of a magnitude insufficient in itself to initiate an arc discharge but sufficient tomaintain an arc discharge within said shielding member after the initiation of the arc discharge.

, 1 LAWRENCE D. MILES.. 

